Apparatus for forming films by evaporation in vacuum

ABSTRACT

An apparatus for forming films by evaporation in vacuum has a chamber for evaporating a coating material containing a coating material (10), and a heating element (2) positioned outside this chamber. A collimating chamber (3), which is identically constructed, communicates with the chamber (1), and each of the chambers (1,3) has a pair of ports (4, 5) aligned on an axis (8), a socket pipe (6,7) being received in one of the ports, respectively, the socket pipe (6) of the evaporation chamber (1) being received in the port (5) of the collimating chamber (3), the evaporation chamber (1) having a sealing member (9) provided in the other port (4) of the chamber (1).

FIELD OF THE INVENTION

The invention relates to the technique of coating by evaporation invacuum, and, more specifically, it deals with an apparatus for formingfilms by evaporation in vacuum.

An apparatus for forming films by evaporation in vacuum, preferably ofvaluable materials such as gold, silver, platinum, palladium may be usedin the electronic and radio engineering and in acoustics, in themanufacture of e.g. integrated circuits as well as in metal coating andin tuning of quartz resonators in vacuum.

The most promising nowadays is a technique of forming films byevaporation on vertically positioned substrates as it is capable ofensuring maximum yield of normal grade products owing to aninsignificant contamination of substrates in comparison with methodsinvolving horizontal position of substrates. The main requirementsimposed upon apparatuses for forming films by evaporation in vacuum arehigh uniformity of film thickness and low losses of a coating materialwith a simple construction of the apparatus.

BACKGROUND OF THE INVENTION

Known in the art is an apparatus for forming films by evaporation invacuum (GB, B, 1517085), comprising a debiteuse containing a materialbeing evaporated, the electric current flowing directly through thedebiteuse for heating and evaporating a coating material. A substrate isplaced horizontally opposite to the debiteuse and is spaced therefrom.

This apparatus is characterized by large losses of a coating materialbecause of the absence of a directional flow of the evaporated material,and it can only be used for forming films on horizontal substrates.

For creating a directional flow of an evaporated material, nozzles areused, e.g. in an evaporator for vacuum plants (SU, A, 397567) having aheater accommodating a crucible containing a material to be evaporatedand a nozzle provided in the top part of the crucible. A substrate ishorizontally positioned and is aligned with the nozzle axis and spacedfrom the outlet edge of the nozzle.

This prior art evaporator also features availability of a boundary layerin the flow adjacent to the walls of the nozzle, the width of theboundary layer covering a substantial part of the flow with velocitiesof evaporated materials used in practice. Molecules emitted from thislayer move chaotically and cause an increase in losses of a coatingmaterial.

A substantial reduction of losses of a coating material can be achievedby using the technique of solid phase recovery of an evaporated materialthat failed to get to the substrate as it is the case in an apparatusfor forming films by evaporation in vacuum (U.S. Pat. No. 4,700,660),comprising a chamber for evaporating a coating material, a heatingelement provided outside the chamber, and a collimating chambercommunicating therewith, each chamber of identical construction havingtwo ports aligned on one and the same axis.

The chamber for evaporating a coating material and the collimatingchamber comprise a pipeline having a transverse plane of symmetry. Thebottom end of the evaporation chamber is positioned in a cruciblecontaining a coating material. Both chambers may be separated by adiaphragm with an opening extending in the plane of symmetry.

The pipeline is turned over at regular intervals as the coating materialis consumed and replenished and is placed in such a manner that itshould be received in the crucible with an end thereof on which thecoating material that failed to get to the substrate has been deposited.This material is used in the next evaporation cycle.

The abovedescribed apparatus is, however, suitable for forming filmsonly on horizontally positioned substrates as the coating material canflow out through unsealed spots in the joint between the bottom end ofthe pipeline defining the evaporation chamber and the crucible. Inaddition, in the simplest versions of the apparatus in which thepipeline is of an integral construction and has an annular recess in themiddle part separating the evaporation and collimating chambers, thematerial is always condensed in the annular recess zone with anyposition of the pipeline. The coating material collected in the annularrecess would overflow to one of the chambers so as to cause anasymmetric change in distribution of intensity of vapour flow escapingfrom the collimating chamber thus lowering uniformity of thickness ofthe applied films.

In addition, this apparatus in its simplest form cannot ensure highuniformity of thickness of the applied film on large-area substrateseven if they are positioned horizontally, and the use of variousdiaphragms provided for that purpose in the pipeline complicatesconstruction of the apparatus.

In case rather thick films are to be formed, a layer of materialcondensed in the collimating chamber causes a change in distribution ofintensity of vapour flow escaping therefrom thus lowering uniformity offilm thickness.

Moreover, evaporation of the coating material simultaneously from thecrucible and evaporation chamber which are generally at somewhatdifferent temperatures results in a change in evaporation rate duringevaporation: first evaporation of the material occurs at a higher ratefrom a stronger heated surface (evaporation chamber) and then thematerial evaporates at a lower rate from a less heated surface(crucible). For ensuring a parity between evaporation rates, it isnecessary to control heating current during evaporation which makes theapparatus more complicated.

SUMMARY OF THE INVENTION

The invention is based on the problem of providing an apparatus forforming films by evaporation in vacuum having such a relative positionof the evaporation and collimation chambers and such a constructionthereof as to ensure film forming with uniform thickness and with lowlosses of a coating material with vertically positioned substrates.

The above problem is solved by that in an apparatus for forming films byevaporation in vacuum, comprising a chamber for evaporating a coatingmaterial having a heating element positioned outside thereof andcommunicating with a collimating chamber, both chambers beingidentically constructed and each having a pair of aligned ports,according to the invention, the axis of the ports extends horizontally,the chamber for evaporating a coating material and the collimatingchamber are each provided with a pipe socket positioned in one of theports, the pipe socket of the chamber for evaporating a coating materialbeing received in the other port of the collimating chamber, the chamberfor evaporating a coating material having a sealing member provided inthe other port thereof, the coating material being contained directly inthe chamber for evaporating a coating material.

The apparatus preferably has a directional vapour flow former comprisinga rod aligned with the axis of the ports of the chamber for evaporatinga coating material and attached to the sealing member thereof.

The distal end of the rod is preferably received in the pipe socket ofthe chamber for evaporating a coating material be define a space withits inner surface

The distal end of the rod is preferably positioned adjacent to the innersurface of the pipe socket of the chamber for evaporating a coatingmaterial and has an axial passage and a plurality of ports in theperiphery of the rod communicating therewith.

It is also preferred that the apparatus comprises an additional heatingelement extending outside, and along the periphery of the pipe socket ofthe collimating chamber.

The sealing member is preferably made integral with the main heatingelement.

The apparatus for forming films by evaporation in vacuum, according tothe invention, makes it possible to carry out treatment of verticallypositioned substrates thus enhancing uniformity of coated structures andincreasing the yield of normal grade products. High uniformity ofthickness of a coated film with a lower material consumption is therebyensured. The apparatus is simple in construction and reliable inoperation.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described in detail with reference to specificembodiments illustrated in the accompanying drawings, in which:

FIG. 1 schematically shows a general view of an apparatus for formingfilms by evaporation in vacuum in a longitudinal section view, accordingto the invention;

FIG. 2 is ditto of FIG. 1, with a former of a directional vapour flow ina longitudinal section view, according to the invention;

FIG. 3 is ditto of FIG. 2 showing another embodiment of the former of adirectional vapour flow, with a sealing member integral with a heatingelement and with an additional heating element in a longitudinal sectionview, according to the invention.

BEST MODE OF CARRYING OUT THE INVENTION

An apparatus for forming films by evaporation in vacuum comprises achamber 1 (FIG. 1) for evaporating a coating material, a heating element2 positioned outside thereof, and an identically constructed collimatingchamber 3 communicating with the evaporation chamber. The chambers 1, 3have ports 4, 5 and pipe sockets 6, 7. The ports 4, 5 and pipe sockets6, 7 are aligned on one and the same horizontal axis 8 which in thisembodiment of the apparatus extends somewhat above the axis of symmetryof the chambers 1, 3. To establish communication between the chambers 1and 3, the pipe socket 6 of the evaporation chamber 1 is received in theport 5 of the collimating chamber 3. The evaporation chamber 1 has asealing member 9 provided in the port 4, e.g. using a threaded joint(not shown in the drawing).

A coating material 10 is contained directly in the evaporation chamber 1and its level should not be above the lower edge of the port 4.

The heating element 2 maintains a temperature for evaporation of thecoating material 10 in the evaporation chamber 1, and temperature in thecollimating chamber 3 is below melting point of the coating material 10.The chamber 3 is designed for a solid-phase recovery of the evaporatedmaterial 10 that failed to pass through the pipe socket 7.

A substrate 11 for forming a film thereon is positioned in a spacedrelation to the outlet opening of the pipe socket 7 along the axis 8.

The identity of the chambers 1 and 3 makes it possible to exchange themso as to return the material 10 condensed in the collimating chamber 3for re-evaporation.

The fact that the pipe socket 6 of the evaporation chamber 1 is receivedin the port 5 of the collimating chamber 3 rules out vapour ingress intothe joint between the chambers 1, 3 so as to prevent the chambers 1, 3from being soldered together with the melt of the coating material 10and avoid losses of the coating material.

In this embodiment the sealing member 9 is mounted on a pin 12 (FIG. 2)attached to an arm 13 provided in a vaccum chamber (not shown in thedrawing). The chambers 1 and 3 are pressed against the sealing member 9by a spring 14 secured to the arm 13 by means of a screw 15 so as toensure reliable sealing of the port 4 even with a thermal expansion ofthe sealing member 9 and evaporation chamber 1.

A directional vapour flow former in the form of a rod 16 extending alongthe axis 8 is provided on the sealing member 9. The distal end of therod 16 is received in the pipe socket 6 with a space 17 definedtherebetween. Vapour flow escaping through the annular space 17 ensuresa more uniform thickness of a film formed on the substrate 11. The endof the rod 16 as well as the pipe socket 6 may have a differentconfiguration, e.g. conical (not shown in the drawing) so as to ensureinuformity of film thickness on the substrate 11 of a large size.

The chambers 1, 3, sealing member 9 and rod 16 may be made of graphiteor of a high melting metal such as molybdenum. The heating element 2 mayalso be made of a high-melting sheet metal and secured to current leadsof the apparatus (not shown in the drawing).

In another embodiment of the apparatus shown in FIG. 3, the distal endof the rod 16 is positioned adjacent to the inner surface of the pipesocket 6 of the evaporation chamber 1. In this case the rod 16 has anaxial passage 18, and a plurality of ports in the periphery of the rod16 communicating therewith.

In this embodiment of the apparatus there is provided a second heatingelement 20 positioned outside, and along the periphery of the pipesocket 7 of the collimating chamber 3. It may also be made of ahigh-melting metal and connected to current leads (not shown in thedrawing). The heating element 20 ensures a temperature rise of the pipesocket 7 above melting point of the coating material 10 at regularintervals (FIG. 1) for returning the material to the collimating chamber3 so as to coat the substrate 11 with a thicker film without impairingits quality.

In this embodiment the heating element 2 (FIG. 3) is made integral withthe sealing member 9 so as to guarantee the heating of the sealingmember 9 which should be at a temperature at least equal to that in theevaporation chamber 1.

The heating element 2 has taps 21 and 22 to attach it to current leads(not shown in the drawing). A slit (not shown in the drawing) is madeaxially along the heating element 2 to ensure an optimum distribution ofelectric current over the whole surface of the heating element 2. Theheating element 2 and the sealing member 9 and taps 21, 22 may be madeof graphite.

The evaporation chamber 1 may be connected to the sealing member 9 bymeans of a threaded joint ensuring a reliable sealing of the chamber 1.The collimating chamber 3 is mounted on a support 23, and a thermalscreen 24 made of a high-melting sheet metal is provided adjacent to theheating element 2 and sealing member 9 to reduce heat radiation.

The apparatus for forming films functions in the following manner.

The coating material 10 is charged in the chamber 1 for evaporation(FIG. 1). After placing the support 11 and the whole apparatus into avacuum chamber (not shown in the drawing), air is evacuated therefrom toa working pressure. Then the heating element 2 is switched on.Temperature in the evaporation chamber 1 increases, and the material 10available therein is heated to a temperature necessary for itsevaporation. The resultant vapour escapes through the pipe socket 6 anda part of it passes through the pipe socket 7 to be deposited on thesubstrate, the part that failed to get to the substrate 11 beingcondensed on the inner surface of the collimating chamber 3.

After forming a film of the desired thickness on the substrate 11, theheating element 2 is switched off. Then the coating material 10 ischarged into the collimating chamber 3 if necessary, and the chambers 1and 3 are exchanged. Thus, the coating material 10 deposited on thewalls of the collimating chamber 3 is used in the next coating cycletogether with the fresh-charged material.

The apparatus in which the sealing member 9 and chambers 1, 3 aremounted on the arm 13 (FIG. 2) by means of the pin 12 and spring 14functions in the same manner. This apparatus ensures a more uniform filmthickness as vapour flow escaping through the space 17 and having anannular configuration turns into a solid-section flow as it passesthrough the collimating chamber 3. The peripheral areas of the flow arecondensed on the walls of the chamber 3, and the central portion thereofreaches the substrate 11 to form a uniform thickness film thereon. Thisapparatus having the rod 16 the end of which is received in the pipesocket 6 to define a space 17 is preferably used for forming films onlarge-size substrates with the ratio of their diameter to the distancefrom the pipe socket 6 greater than 0.4.

The apparatus shown in FIG. 3 functions in a similar manner. Thedistinguishing feature of this apparatus resides in that the evaporatedmaterial is admitted from the evaporation chamber 1 to the collimatingchamber 3 through the ports 19 in the periphery of the rod 16 and axialpassage 18 of the distal end of the rod 16. After the escape from thepassage 18, a directional diverging vapour flow is formed so as toenable formation of films on substrates 11 of various sizes.

If a film of a large thickness is to be formed on the substrate 11, theheating element 20 is switched on at regular intervals during coating soas to melt the layer of the coating material deposited in the pipesocket 7 and to cause it to overflow to the collimating chamber 3 toprevent the inside diameter of the pipe socket 7 from decreasing whichmight result in a lower coating rate and impaired uniformity of filmthickness.

Therefore, the apparatus for forming films by evaporation in vacuum,according to the invention, allows films to be formed on verticalsubstrates and ensures high uniformity of film thickness with a lowmaterial consumption.

INDUSTRIAL APPLICABILITY

The apparatus for forming films by evaporation in vaccum preferably ofvaluable materials such as gold, silver, platinum, palladium may be usedin the electronic and radio engineering and acoustics, e.g. in themanufacture of integrated circuits as well as for metalcoating and fortuning of quarz resonators in vacuum.

We claim:
 1. An apparatus for forming films by evaporation in vacuum,comprising a chamber (1) for evaporating a coating material, a heatingelement (2) provided outside the evaporation chamber, and a collimatingchamber (3) communicating therewith, the chambers being identicallyconstructed and each having a pair of ports (4, 5) which are aligned onone and the same axis (8), characterized in that the axis (8) of theports (4, 5) extends horizontally, the chamber (1) for evaporating acoating material and the collimating chamber (3) each has a pipe socket(6, 7) positioned on one of their ports, the pipe socket (6) of thechamber (1) for evaporating a coating material being received in theother port (5) of the collimating chamber (3), the chamber (1) forevaporating a coating material being provided with sealing member (9)provided in the other port (4) thereof, the coating material (10) beingcontained directly in the chamber (1) for evaporating the coatingmaterial.
 2. An apparatus for forming films by evaporation in vaccum,according to claim 1, characterized in that it comprises a directionalvapour flow former in the form of a rod (16) positioned along the axis(8) of the ports (4) of the chamber (1) for evaporating the coatingmaterial and attached to the sealing member (9) thereof.
 3. An apparatusfor forming films by evaporation in vaccum according to claim 2,characterized in that the distal end of the rod (16) is received in thepipe socket (6) of the chamber (1) for evaporating the coating materialto define a space (17) with its inner surface.
 4. An apparatus forforming films by evaporation in vacuum according to claim 2,characterized in that the distal end of the rod (16) is positionedadjacent to the inner surface of the pipe socket (6) of the chamber (1)for evaporating the coating material, the rod (16) having an axialpassage (18) and a plurality of ports (19) in the periphery of the rod(16) communicating with its axial passage.
 5. An apparatus for formingfilms by evaporation in vacuum according to claim, characterized in thatit comprises an additional heating element (20) positioned outside, andalong the periphery of the pipe socket (7) of the collimating chamber(3).
 6. An apparatus for forming films by evaporation in vacuumaccording to claim 1, characterized in that the sealing member (9) ismade integral with the main heating element (2).
 7. An apparatus forforming films by evaporation in vacuum according to claim 5,characterized in that the sealing member (9) is made integral with themain heating element (2).